1. Field of the Invention
This invention relates to a pulse width modulated dimming system in a vehicle, more particularly to a dimming system for manually controlling the dimming of the intensity of the light from the panel lamps with respect to full intensity using a pulse width modulated control signal.
2. Prior Art
In controlling the amount of current routed to the lamps in the instrument panel, a field effect transistor (FET) is usually employed. Some sort of charge pump/voltage doubler network is used to develop power for driving the FET. To develop the power a rather high frequency pulse width modulated (PWM) signal is commonly used to stimulate the charging of the capacitors in the charge pump circuit. However, in using the high frequency PWM signal undesirable system noise develops and usually more than one capacitor and often many other components such a schmitt triggers must be used to fulfill the charge pump operation.
Realizing the various problems associated with high speed switching of signals in various high reactance media and keeping cost of components in vehicles at a minimum without sacrificing performance, a search was initiate for various means to provide control over PWM dimming of lamps. This search resulted in the improved PWM dimming system of the present invention.